Timing mechanism



March 29, 1938. E. D. MEAD 2,112,375

TIMING MECHANISM Filed March 10, 1936 8 Sheets-Sheet l INVENTOR E. D.MEAD A T TORNE V March 29,1938. E, D, MEAD 2,112,375

TIMING MECHANISM Filed March 10, 1936 8 Sheets-Sheet 2 A 7' TOR/VEV E.D. MEAD TIMING MECHANISM March 29, 1938.

1936 8 Sheets-Sheet Filed March 10,

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lNl EN 70/1 E. D. MEAD A T TORNEV March 29, E. D MEA TIMING MECHANISMFiled March 10 8 Sheets lNVENTO/Q E. D. MEAD FIG. /7

ATTORNEY E D. MEAD March 29, 1938.

TIMING MECHAN I$M Filed March 10, I936 8 Sheets-Sheet A T TOPNEV March29, 1938. E D. D 2,112,375

TIMING MECHANISM Filed March 10, 1936 8 Sheets-Sheet 6 tr/5 MINUTESW 3M/NUTE$- fez-v5 .V HOLDING Afi con/mar; "H"

m r OFF-NORMAL CONTACTS?" 4 1 CONTACTS m m r 222 GROUND CONTACTS F" ALock/N6 CONTACTS "a" INVENTOR 0. MEAD BV A 7' TORNEV March 29, 1938. E.D. MEAD 2,112,375

TIMING MECHANISM Filed March 10, 1936 8 Sheets-Sheet 7 INVENTOR By 5.0.MEAD A T TORNEV March 29, 1938. E. D. MEAD 2,112,375

TIMING MECHANISM Filed March 10, 1936 8 Sheets-Sheet 8 .mll. bvw

A 7" Tom/EV Patented Mar. 29, 19 38 a i I UNITED STATES PATENT OFFICETIMING MECHANISM Edward D. Mead, Caldwell, N. I, assignor to BellTelephone Laboratories, Incorporated, New

York, N. Y., a corporation of New York Application March 10, 1936,Serial No. 68,073

11 Claims. (Cl. 16119) This invention relates to timing mechanisms formapplicable for a telephone connection where and particularly to devicesof this character used the charging rate for the initial period differsfor measuring intervals of conversation in a telefrom the charging ratefor an overtime period of phone system to determine thereby the approthesame duration each. timing unit has one priate charge for the servicerendered. The ingear wheel engageable with the constant speed vention isapplicable not only to local calls from shaft for measuring the initialperiod and a secsubscribers' lines or coin box lines where the 0nd gearwheel engageable with said shaft after charges may be uniform for theinitial period and the completion of the initial period for measuringeach overtime period but is also applicable where any overtime periodand for closing the charging the charges depend upon the zone called aswell circuit in accordance with the number of revolu- 10 as the durationof the call. tions required to measure the overtime period.

An object of the invention is to simplify and Tensioned spring means maybe employed for improve devices used for measuring and indirestoringeach wheel to normal after the given eating intervals of time to renderthem more connection has been broken. Other features of accurate andreliable in their operation and to the invention will appear in thefollowing de- 15 render them capable, with only minor alterations,tailed description.

of assessing charges according to a variety of re- Referring to thedrawings: quirements with respect to initial and overtime Fig. 1 is anassembly view of the timing mechcharges. anism for local telephone callsillustrating the The timing mechanism of this invention is pardrivingshaft and the manner in which the several ticularly applicable for usewith the message regtiming units are mounted; ister circuits disclosedin the copending applica- Fi 2 s a top Vi Of 0116 Of e t ming units;tion of F. J. Scudder Serial No. 68,044, filed March Fig. 3 is a sideviewand Fig. 4 an end view 10, 1936, issued as United States Patent2,089,438 of one of these units;

- on August 10, 1937. Fig. 5 is an end view of the armature hinge of Inits preferred form, the invention utilizes a common driving shaft whichmay be rotated at a 6 is an enlarged e in perspective of an constantspeed and a number of electromagnetic arrangement for keep under on tdevices having timing elements which are arsion the restoring spring forthu rotatable memgg ranged to be engaged with' and disengaged from herof the timing unit; the driving shaft much in the manner disclosed F g 7and 8 illustrate the apparatus of 6 in my earlier Patent No. 1,993,793issued March in difierent positions;

12, 1935. Fig. 9 is an alternative to the apparatus of Eachelectromagnet has an armature which is actuated when a given telephoneconnection is Fig. 10 is a diagram illustrating the manner 35established to move a slidable pinion on the Of pera 0 t e timing unitelectrical Contacts driving shaft into engagement with a gear wheel duing a COHVBISatiOH period being measured of a suitable timing unit. Theconsequent roy; tation of the gear wheel controls the timing and S- 1116, inclusive, are Schematic OiMW" charging functions in accordance withthe circuit ng illustrating the timing device in its Various 40requirements. In one form of the invention ap- S a s of Operation;plicable for a telephone connect on where the Fig- 17 is an assemblyView Of another yp o charging for the initial period is the same as fortimin mechanism for zone calls where the an overtime period of the sameduration, the said char in for t e overtime period is on a differentgear wheel is adapted to rotate as many revolubas s t a t e initialperiod; 45 tions as needed to measure a given call, closing Fig. 18 is atop V 19 a S de View and the charging circuit shortly after thebeginning Fig. 20 an end view of one of the timin units of of eachrevolution. A tensioned spring serves to restore the gear wheel to itsnormal position after Figs. 21 and 22 are bottom views of the timing tothe connection has been broken and special unit of Fig. 18; a means areprovided for maintaining a substan- Fig. 23 is an "nlarged sectionalview of a part tially constant tension on said spring when said of thetiming unit of Fig. 18; wheel makes more than one complete revolutionFig. 24 illustrates details of the overtime measin the measurement or agiven connection before uring element of Fig. 18; being returned to itsnormal position. Inanother Figs. 25 and 26 are end view: of the gear 55wheel of the initial period charging unit of Fig. 18;

Figs. 27 and 23 illustrate details of the restoring spring restrainingmeans;

Fig. 29 is a diagram illustrating the manner of operation of theelectrical contacts of the timing unit of Fig. 18 during a conversationperiod being measured thereby;

Figs. 30 to 3'7, inclusive, are schematic drawings illustrating thetiming device of Fig. 18 in its various stages of operation; and

Fig. 38 shows a portion of a machine switching system of the cross-bartype utilizing a local timing unit assembly of the type of Fig. land azone timing unit assembly of the type of Fig. 17.

A detailed description will first be given of the timing device of Figs.1 to 16, inclusive. This device (Fig. l) comprises a mounting frame I onwhich is supported a driving motor 2 and also a shaft 3. The motor 2 isconnected to shaft 3 by means of gear wheels 4 and 3. Motor 2 isarranged to be operated at a constant speed so that the rotation ofshaft 3 may serve to accurately measure intervals of time. Frame I alsosupports a plurality of timing elements only two of which are shown asindicated generally by the reference character 3. The driving shaft 3 isI equipped with a series of slidable pinions 1 one for each timingelement, and the pinions are keyed to the shaft in the longitudinalgroove 3. Each pinion 1 is adapted to be moved into engagement with-thegear wheel forming a part of the corresponding timing element.

The individual timing element, the details of which are shown moreparticularly in Figs. 2 to 6,

comprises a bracket 3 supported by the main frame I and supporting afixed shaft l3 on which is rotatably mounted a large gear wheel I I.This gear wheelll is normally disengaged from its driving pinion butwhen its driving pinion I 'is moved a short distance to the left asviewed in Fig. 1 the teeth of the gear wheel mesh with the teeth l2 onits driving pinion, thereby rotating the wheel II as long as it is inengagement with its pinion.

Gear wheel ii is normally biased to a zero position by a tensionedhelical spring l3 which tends to keep a lug l1 on the wheel against aspring stop l3 (Fig. 2), that is, the restoring spring l3 tends torotate wheel clockwise as viewed in Figs. 3 and 6. Referring moreparticularly to Fig. 6, one end l3 of this restoring spring is heldagainst a shoulder 23 of a collar 2| fastened to fixed shaft i3. Theother end 22 of the helical spring is suitably fastened to the innerface of wheel I I so that the counter-clockwise rotation of wheel (Fig.6) by its pinion 1 tends to wind up the helical spring as the rotationcontinues. Attached to wheel II and rotatable therewith is an elongatedsleeve 23 surrounding the fixed shaft l3 and acting as a support or,guide for the turns of the spring. The first fewturns of the springadjacent wheel II are supported on the collar 24 of sleeve 23 whileintermediate turns are 51101- mally out of contact with sleeve 23. Theouter turns of the helical spring rest on a sleeve 23 formed as a partof stationary collar 2|. The outer end of sleeve 23 freely rotateswithin the stationary sleeve 23. Located on the outer end of fixed shaftI3 is a nut 23 having an inner shoulder 33 acting as a bearingfor anannular ring-shaped cam 3| having two upwardly extending projections 32,33 and an arcuate slot 34 normally containing end l3 of helical springl3. Cam 3| is driven by a tongue 33 projecting from a bracket 33fastened to the inner face of the gear wheel II. The purpose of cam 3|is to .maintain a substantially constant tension on helical spring I3 inspite of the number of complete revolutions made by wheel II in timing agiven telephone connection as will be explained later. Also mounted onbracket 33 is an annular ring 31 which supports a flexible cam 33 foroperating certain electrical contacts to be described later. For thepurpose of operating still other electrical contacts there is mounted onthe inner face of wheel I a cam 39-.

Each timing unit has an electromagnet 42 best seen in Fig. 3. One end ofits armature 43 rests upon the flattened portion 43 of the magnet coreand the armature is hinged by two non-magnetic spring strips 44, 43(Figs. 3 and which are riveted to the corners of the rear end of thearmature and are clamped to core portion 43. These springs 44, 43 aregim an initial bias so that when they are clamped to the core they pressthe rear end of the armature firmly against the core to avoid magneticleakage while still affording a knife edge pivot for the armature.

Armature 43 carries a spring member 43 (Fig. 3) having a tongue 41 whichrides in the annular groove 43 in its associated pinion 1. When theelectromagnet 42 is energized the movement of armature 43 to the left asviewed in Fig. 2 is suiiicient to cause the teethon pinion 1 to engagethe teeth on wheel II and start the rotation of wheel II in acounterclockwise direction as viewed in Fig. 3, wheel before engagementwith pinion 1 being in a definite zero position as determined by lug |1against spring stop l3. It is, of course, to be assumed thatelectromagnet 42 is energized at the moment the called station hasanswered and that electromagnet.42 is deenergized when the connection isbroken so that the amount of rotation of wheel while electromagnet 42 isenergized is a measure of the duration of the telephone connection andcan be utilized in making the appropriate charges therefor.

The bracket 3 supports a plurality of electrical spring contacts whichwill be best explained by reference to Figs. 2 and 11 both of which showthe gear wheel I I in its normal zero position with lug l1 againstspring stop l3. The subsequent Figs. 12 to 16 show the wheel II and itsrelated apparatus in other relative positions. With the electromagnet 42deenergized its armature 43 is maintained in its outer position by aspring 43 acting against the armature. Spring contact 33 is normallybiased to make electrical contact with the stiff contact spring 3|,contacts 33, 3| being termed the ground contacts D. Spring 33 carries alug 32 projecting towards the flexible cam 33 carried by the bracket 33on wheel II but the normal path of movement of cam 33 does not lie inthe pathof lug 32. However, armature 43 carries a roller 33 with whichthe flexible cam 33 will contact when the wheel I I is rotatedcounterclockwise to throw cam 33 into the path of lug 32 to cause spring33 to break its contact with member 3| and make contact with the spring33. Contacts 33, 33 are termed the charging contacts C.

The spring pile-up also includes two stlf! springs 31 and 33 and twoflexible springs 33, 33. Flexible spring 33 is normally biased to makecontact with stiff spring 31 but when the wheel II is in its zeroposition as in Fig. 11 the cam 33 on wheel presses against a lug 3|mounted on spring 33 to keep electrical spring contacts 31, 33 separatedas long as wheel H is in its zero position. Lug 3| also has an'extension 32 which serves to press the flexible spring contact 33 totime.

against spring 60 as long as cam 39 is opposite lug 6|. Contacts 51, 58are hereinafter termed the holding contacts A and contacts 59, 60 theoff-normal contacts B. Therefore, with the wheel H in its zero positionagainst stop l8, the holding contacts A are open, theoil-normal contactsB are closed, the charge contacts C are open and the ground contacts Dare closed. The functions of these contacts will be described brieflylater but for a more detailed description reference is made to theScudder application mentioned above. 4 v

When the electromagnet 42 is energized its armature 43 acting againstretracting spring 49 brings pinion 1 into engagement with the gear wheelH and also by means of roller 55 bends flexible cam 38 into the path oflug 52 on spring 50. The armature is shown in its actuated position inFig. 12 whereupon the gear wheel H starts turning in the directionindicated by the arrow. Shortly after the turning movement has started,cam 39 rides 01f lug 6| and flexible spring 58 is then free to followits natural bias to close holding contacts A and open the off-normalcontacts B as shown in Fig, 13. Contacts A remain closed and contacts Bremain openuntil cam 39 has again reached lug 6 I. Shortly after theholding contacts A have been closed the flexible cam 38 contactsmomentarily with lug 52 to open the ground contacts D and close thecharging con tacts C as shown in Fig. 14. As soon as lug 52 becomes freeof flexible cam 38 the flexible spring 5!] follows its natural bias toopen the charging contacts C and close the ground contacts D as shown inFig. 15. The condition of the contacts shown in Fig. 15 holds during thegreater part of acomplete revolution of wheel ll. Fig. 16 shows thecondition just before wheel l i has finished a complete revolution andone complete revolution will have taken place as soon as wheel I I hasmoved far enough from its position of Fig. 16 to allow spring stop it todrop behind the rear edge of lug [1. It will be apparent from Fig. 16that just prior to the completion of one revolution of wheel ll, lug 6irides up on cam 39 to again open holding contacts A and close onnormalcontacts B.

It will be apparent that gear wheel ll may make only a partialrevolution or as many complete revolutions as are needed for timing theparticular telephone connection for which the timing unit has beenselected. If the telephone connectionelasts for a time corresponding toless than one complete revolution of wheel ll it will be apparent thatthe charging contacts C will be operated only once but if the telephoneconnection continues for a fraction of an additional turn of wheel H thecharging contacts will again be actuated as it will be seen from Fig. 16that only a small additional movement of flexible contact'38 is neededto cause the second closing of the charging contacts C,

The diagram of Fig. 10 illustrates the manner in which the contacts areoperated with respect In Fig. 10 it is assumed that the time requiredfor a complete revolution of wheel H is five minutes and that thecharging contacts are to be operated once for each five-minute period orfraction thereof. The two vertical lines Si and 58 are intended torepresent the duration of a five-minute period where vertical line 61represents the beginning of the period with wheel I l. in zero position,and vertical line 38 represents the end of the five-minute period withthe wheel having completed exactly one revolution. Lines 63, 64, 65 and56 represent the condition during the measured period of the holdingcontacts A, the off-normal contacts B, the charging contacts C and theground contacts D, respectively. It will be seen that shortly after thebeginning of the measured period the holding contacts are closed and theoif-normal contacts are opened and they continue in their alteredposition until just prior to the elapse of the five-minute period whenthe holding contacts are opened and the off-norn1al contacts closed. Atthe beginning of the initial period and shortly after the holdingcontacts and off-normal contacts are operated the charging contacts Care momentarily closed, accompanied by the momentary opening of theground con tacts D. If the measured period extends beyond the initialfive-minute period it will be obvious that the contacts again areoperated in the same manner as at the beginning of the initial period.

As previously stated, the timing unit of this L invention as abovedescribed contemplates having gear wheel ll make one complete revolutionfor the initial period of a conversation being measured and to have thewheel make as many additional revolutions or fractions thereof as areneeded to measure the overtime period. It is, therefore, necessary toprovide means for preventing the restoring spring l6 from becoming woundtoo tightly. Preferably, automatic means are provided for unwinding thehelical spring l6 one turn whenever the wheel II by its rotation haswound the spring up substantially one turn. A preferred arrangement isdisclosed in Figs. 6, '7 and 8. As previously described, with referenceto Fig. 6, one end of helical spring is fastened to 1.

wheel ii and the other end lics against the sta tionary stop 20 so thatas the wheel ll revolves counter-clockwise the spring is wound up. Thenormal position for driving tongue 35 with the wheel in zero position isadjacent shoulder 32 of cam ring 3i as shown in Fig. 3. Fig. 6 showswheel it after it has been rotated about 90 degrees from its normalposition as indicated in that figure by the angular relation of springstop 98 to lug ll. volving counter-clockwise under the action of pinionl tongue 35 moves with the wheel and after the wheel has moved about 90degrees as shown in Fig. 6 the tongue 35 contacts with shoulder 33 androtates cam ring 3| along with the wheel. Tongue'35 continues to drivecam ring 3i counter-clockwise and finally reaches the position shown inFig. 7 where the wheel has completed one revolution and has also turnedthrough a small fraction of another revolution. At this position of big.7 cam surface ll contacts with end iii of the helical spring and withthe further counter-clockwise movement of cam ring 3! as shown in Fig. 8raises the spring end i9 over the top of stationary stop 29 therebyfreeing that end of the spring and alldwing it to start unwinding.However, spring end [9 in flying around the nut 29 enters slot 36 in thecam ring and pushes cam ring 3| forwardly until the spring end againcomes to rest against stop 20. The spring, therefore, unwinds only oneturn at a time and will not unwind another turn until the wheel II hascompleted another revolution from its position in Fig. 8. If the wheel His disengaged from its driving pinion 7 prior to the completion of itsfirst revolution it will be obvious that whatever winding-up of springl6 took place will be annulled by the clockwise restoring movement ofthe wheel. If we assume that the wheel I1 is disconnected from itsdriving pinion when When the wheel ll starts refrom its zero positionthrough an angle indicatedby the difference in the positions of shoulder33 in Figs. '7 and 8. In order that this unwinding mechanism may beeffective without impairing.

the main function of the spring to supply a restoring force to returnthe wheel I I to its normal position, a lost motion connection betweendriving tongue 35 and cam ring 3| is desirable. The arcuate slot 34should'extend far enough towards shoulder 33 that there will be nodanger when tongue 35 is against shoulder 32 that spring end l3 willcontact with the closed end of slot 34 instead of stop 28.

An alternative form of the unwinding mechanism for the helical spring isshown in Fig. 9. The portion of a timing unit shown in Fig. 9 isidentical with that disclosed in the earlier figures except for theunwinding mechanism. The gear wheel 1 is shown turned substantially 90degrees counter-clockwise from its zero position which is determined byhaving lug 16 against spring stop 11. Wheel 15 is suitably mounted forrotation about a fixed shaft 18 and the wheel 15 carries a drum 18 aboutwhich is wrapped the helical restoring spring 88 one end of which isfastened to wheel 15 and the other end 8i passes over a stationary nut82 and is held against a shoulder 83 on said nut. The outer end of drum1!! is cut away to form a bearing for a cam ring 84 which has a camsurface 85 and an arcuate shaped arm 88 above an elongated slot 81. Theouter edge of drum 19 which is of reduced diameter to support the camring 84 also has a radial wedge-shaped slot defined by shoulders 88 and98 therein into which fits loosely a projection 89 from the inner sideof the cam ring 84. With wheel 15 in its zero position, projection 88 isnormally adjacent shoulder 98. As the wheel begins rotatingcounter-clockwise, projection 88 advances until it strikes shoulder 88and thereafter the cam ring is rotated with the wheel 15, whichrotation, if continued more than a complete revolution, will cause camsurface 85 to contact with spring end 8| and raise the end of the springover the top of stop 83 thereby allowing the spring to unwind one turnin the same manner as described for Fig. 6. The main difference betweenFigs. 6 and 9 is in the manner of actu- Ming the cam which temporarilyfrees the spring end from its retaining stop. Further description ofFig. 9 is, therefore, believed unnecessary.

A detailed description will now be given of an alternative form of thetiming mechanism disclosed in Figs. 1'1 to 3'1. The timing mechanism ofthese figures is particularly designed for use in operating messageregisters where the charge for and the duration of each overtime periodmay be different from the charge for and duration of the initial period.

The assemblyof these timing devices for zone calls comprises, as shownin Fig. 17, a mounting frame I88 on which is supported a constant speeddriving motor IN and a shaft I82 connected therewith by suitablegearing. Frame I88 also supports a plurality'of timing units only two ofwhich are shown indicated generally by the reference character I83. Thedriving shaft I82 ad- Jacent each timing unit is equipped with twoslidable pinions I84, I88 keyed to the shaft in the longitudinal grooveI88. The pinions I84 and I85 are adapted to be selectively engaged withgear wheels individual to each timing unit.

The individual zone timing unit the details of.

which are shown more clearly in Figs. 18 to 28 comprises an L-shapedbracket I81 fastened to the main frame I88, said bracket supporting afixed hollow shaft I88 (Fig. 23) on which is rotatably mounted a largegear wheel I83. This gear wheel I88 is normally disengaged from itsdriving pinion I84 but when its driving pinion is moved by meanshereinafterdescribed, the teeth of gear wheel I88 mesh with teeth II8 ondriving pinion I84 thereby rotating wheel I88 until their engagement isbroken. Gear wheel I89 is utilized for timing the initial period whileanother gear wheel H3 is employed for timing any overtime period. Meanshereinafter described are provided responsive to the substantialcompletion of a revolution by wheel I88 for moving pinion I85 so thatits teeth mesh with the teeth of gear wheel I I3 whereby wheel I I3 maybe rotated as many revolutions as required to measure the length of theovertime period.

Referring more particularly to Fig. 23, the overtime wheel Il3 isfastened to a shaft II4 which is rotatably mounted within the fixedhollow shaft I88 and projects beyond it at both ends. The initial wheelI88 does not bear directly on fixed shaft I88 but is 'fastened to oneend of an elongated sleeve II5 which is rotatable about shaft I88.Around sleeve I I5 is a helical restoring spring I I6 one end I I1 ofwhich (Figs. 23, 24) is anchored by insertion in a hole in a rotatableannular disc II8 fastened on sleeve H5, and therefore, rotatabletherewith. Disc II8 may have projecting lugs II9 (Fig. 24) which fitinto slots I28 in. the end of sleeve iii, the disc II8 being held inplace by a threaded collar Hi. The other end I22 of helical spring H8 isheld stationary by passing through a hole in stationary arm I23 (Fig.21). The rotatable sleeve H5 is held in place by a nut I24 threaded onthe end of stationary shaft I88 the opposite end of sleeve II5 bearingagainst shoulder I25.

The rotatable shaft H4 at one end carries the overtime wheel I I3 andits other end has fastened thereto a sleeve I28 which extends beyond theend of shaft II4. Aligned with the axis of shaft II4 but supportedindependently thereof is a stationary pin I21 fastened to a mountingbracket I28. On stationary pin I21 is mounted a sleeve I3I the open endof which overlaps the adjacent end of rotatable sleeve I26. Sleeve I3Iis held in place by a threaded nut I32 having a portion of reduceddiameter which acts as a bearing for a cam member I33. Rotatable sleeveI28 and stationary sleeve I3I act as supports for the tensioned helicalspring I34 used for biasing the overtime gear wheel 3 to its normalposition. One end I35 of the spring is anchored in a hole in a cammember I38 mounted on rotatable sleeve I26 while its other end I31 (Fig.20.) normally lies against a shoulder I38 on sleeve I3I (similar toshoulder 28 of Fig. '7).

Since gear wheel H3 is adapted to rotate any desired number ofrevolutions it, therefore, is necessary to provide means for preventingits restoring spring I34 from becoming wound too tightly and the meansprovided is essentially the same as that of Figs. 6, '1 and 8 in thatthe spring is allowed to unwind one turn every time gear 'agailzst stopI54 (Fig. 20).

7 hit against stop I54, the teeth which rides in groove I68 in pinionI05.

wheel I I3 rotates slightly more than one complete revolution. Fastenedto bracket I36 isa laterally extending arm I39 which extends between twospaced upwardly extending shoulders I40, I4I

(Fig. 19) on cam ring I33 so that the rotation of bracket I36 alsorotates camring I33. This insures that cam surface I42 of cam ring I33once each revolution will serve to lift spring end I31 over shoulder I38to permit the spring to unwind one turn as previously described withrespect to Figs. 6, 'l and 8.

The unwinding arrangement for spring I34 differs in one respect fromthat of Figs. 6, 7 and 8 in that a thin metal collar I45 (Figs. 27, 28)is inserted between stationary sleeve I3I and the last few turns of thespring. This sleeve I45 has an upturned edge I46 with a slot I41 intowhich fits the end I31 of the restoring spring. When cam surface I42lifts spring end I31 over shoulder I38 the spring end is still retainedin slot I41 so that collar I45 rides around with the spring end in theunwinding process. Collar I45 serves to reduce the velocity with whichend I31 travels around nut I32 and. hence reduces the danger that endI31 will 'be broken by the force with which it hits against shoulderI38.

Each timing unit I03 has an .electromagnet I48 (Fig. 19) which isenergized over suitable circuits when the telephone connection isestablished the duration of which is to be measured by the timing unit.Its armature I49 has a spring extension I50 which ridesin a groove inpinion I04 so that the attraction of armature I49 moves pinion I04 intoengagement with initial timing wheel I09. Restoring spring II6 normallyholds initial wheel I09 in its zero position with lug I53 Pinion I04causes the counter-clockwise rotation of initial wheel I09 as viewedfrom the right in Fig. 18. Wheel I09 being used for timing only theinitial period, is adapted to make only one revolution. Just prior tothe time that in the counter-clockwise movement of wheel I09,-lug I53would again on pinion I04 encounter a toothless portion I55 on the wheelperiphery (Fig. 26) so that the driving pinion is no longer effective.This toothless portion,

' however, is bridged by teeth I56 on a separate plate I51 attached tothe wheel, teeth I58 being displaced far enough from the main teeth onwheel I09 that they are not engaged by pinion I04 but are engaged by thegear I58 attached to the speed governor I59 (Fig. 18). The initialtiming wheel I09, therefore, ceases rotation as soon as pinion I04reaches this toothless region at. which time wheel I09 has completedsubstantially one revolution.

Just prior to the completion of the rotation of initial wheel I09 theinitial wheel sets into rotation the overtime wheel H3 in the followingmanner providing, of course, that the conversation to be measured isstill continuing. Initial wheel I09 carries a lug I62 (Fig. 22) whichjust prior to pinion I04 reaching toothless segment I55, contacts with aroller I63 carried byan' arm I64 hinged to frame I 01 by a spring memberI65 which normally biases roller I63 towards wheel I09 against a stopI66 which is an extension of frame I01 (Figs. 21 and 22). An extensionof spring member I85 carries an extension I61 The free end of spring I65is normally biased against an angle piece I69'formed from arm I64. whencam I62 comes into contact with roller I63 the consequent movement ofarm I64 serves to bring teeth I on pinion I05 into engagement with theteeth on gear wheel H3 and start its rotation. Overtime wheel H3 isnormally biased to its zero position with lug I1I against spring stopI12 (Fig. 21) due to its restoring helical spring I34. Wheel I I3 willnow begin rotating to measure the overtime period of the telephoneconnection and will continue rotating as many complete revolutions asare needed. During the movement of wheel II3 spring I34 will unwind oneturn for each complete revolution of the wheel in the same manner asdescribed in connection with Figs. 6 to 8.

Certain electrical contacts are controlled by initial wheel I09 andovertimewheel H3 and the operation of these contacts will now bedescribed with special reference to Figs. 30 to 3'1.

contact spring I89 to contact with the stiff contact spring I90. SpringI90 is biased to press on stud I81 and normally maintain an extension ofspring I81 against a stationary stop I9I. This arrangement normallymaintains open the charging contacts I81, I89 hereinafter called E andnormally maintains closed the ground contacts I90, I89 hereinaftercalled F. Intermediate spring I v89 carries angle piece I92 adapted tobe moved into the path of the toothed charging cam I93 driven by initialwheel I09 and into the path of the toothed charging cam I94 driven byovertime wheel II3.

The stiff contact spring I95 is normally biased against a stationarystop I96 and stiff contact spring I91 is normally biased against studI85 carried by the armature to bias the armature to its non-operatedposition. Hence the attraction of .armature I49 serves to close contactsI95, I91 hereinafter called locking contacts G. Spring I98 is not anelectrical contact spring and its purpose will be described later, butit may be noted that spring I98 is normally biased against stop I86carried by the armature. Contact spring 200 carries a stud I whichpasses through an aperture in contact spring 203 and is pressed againstcam 202 mounted on initial wheel I09 so that theholding contacts Hbetween springs 200, 203 will be closed as soon as cam 202 has movedaway from stud 20I. Stiff contact spring I99 is also biased towardswheel I09 but is restrained by spring projection 204 acting against stud20I. Contact spring 205 has a stud 206 which normally rests on cam 201mounted on wheel H3 and spring 205 has a second stud 208 which passesthrough apertures in springs I99,

closed the off-normal 205 ispressed against tacts I closed. when thetiming unit is seized for the measurement of the duration of anestablished telephone connection the electromagnet I49 is energized toattract its armature I49 as shown in Fig. 31. Armature I 49 whenattracted closes the locking contacts G due to the movement to the leftof stud I99 carried by the armature. Stud I94, also carried by thearmature, contacts with projection H9 and serves to move the threecontact springs I91, I99, I99 to the left to bring projection I92 intothe path of the toothed cams I99, I94 while still preserving the groundcontacts F closed and the charge b'dntacts E open. The attraction ofarmature I49 also brings pinion I94 into engagement with initial wheelI99 which starts rotating in the direction indicated by the arrow.

Shortly after initial wheel I99 starts turning, cam 292 rides oil stud29I, allowing the biased spring I99 to move to the right to open theonnormal contacts I and close the holding contacts H as shown in Fig.32. Cam I99 which is mounted on disc I I9 and which, therefore, rotateswith wheel I99 now comes into contact with projection I92 (Fig. 33) andhence moves spring I99 to the right once for each tooth 2| I on therotating cam I99. This movement serves to temporarily close the chargingcontacts E and term porarily open the ground contacts F and in theparticular timing unit disclosed it will be seen that the chargingcontacts will thus be closed six times, it being assumed that for theparticu lar call being measured the calling station's message registershould be operated six times as the appropriate charge for the initialperiod.

Just prior to the time that pinion I94 reaches the toothless segment onwheel I99 cam 2 I2 comes into contact with spring I99 and spring I99 ispressed to the right by the front sloping edge of cam 2I2. Thearrangement is such that at the moment pinion I94 reaches toothlesssegment I99 of wheel I99 cam 2I2 has caused the maximum movement to theright of spring I99 and the spring is starting to ride down the rearsloping edge 2I9 of the cam. The pressure of spring I99 on cam- 2I2 issumcient to move wheel I99 slightly forward as spring I99 slides downslope 2I9 to positively separate the teeth on pinion I94 from the'lasttooth on wheel I99. That is, spring I99 serves to keep wheel I99 in theposition shown in Fig. 26. Fig. 34 shows wheel I99 in its maximumadvanced position where it will remain until the magnet I49 isdeenergized. Just prior to pinion I 94 reaching toothless segment I99earn 292 again contacts with stud Hi to close the off-normal contacts Iand open the holding contacts H as shown in Fig. 34. Also just prior tothe completion of the movement of wheel I99 lug I92 on wheel I 99 (Figs.20, 22) comes into contact with roller I99 to cause' projection I91 tomove pinion I99 into engagement with overtime wheel II9. as previouslydescribed. Fig. 34, therefore. shows the overtime wheel II9 about toegin its movement.

As the rotation of wheel II9 begins (Fig. 35) cam 291 moves. of! stud299 to open the oi!- nornml contacts I and close the holding contacts Hin a manner previously described. Since electromagnet I49 is stillenergized, projection I92 is still in the path of the toothed cam I94which "as shown in Fig. 23, is a portion of member I99 and hencerotatable with wheel I I9. After wheel II9 has moved an appreciabledistance the toothed cam I94 (Fig. 36) serves to momentarily open theground contacts 1" times and momentarily close the charging contacts Ethree times since there are three teeth on cam. I94. This means that foreach complete revolution of wheel H9 or fraction of a revolution thecalling station's message register will be operated three times, itbeing assumed that such is the appropriate charge for each overtimeperiod.

As overtime wheel I I9 nears the completion of a revolution as shown inFig. 37 stud 299 is moved to the rightby cam 291 to momentarily closethe off-normal contacts I and momentarily open the holding contacts H,but as soon as cam 291 has passed and the wheel II9 has started on itsnext revolution the off-normal contacts I will again "be opened and theholding contacts H again be closed until stud 299 again encounters cam291.

When electromagnet I 49 is deenergized restoring spring II9 will restoreinitial wheel I99 to its zero position with lug I94 against stop I99 andspring I34 will restore overtime wheel II9 to its zero position with lugI1I against spring stop I12 as shown in Fig. 30. The retraction ofarmature I49 withdraws pinion I94 and pulls spring I99 out of .the pathof cam 2I2 to allow restoring spring ll9'to restore wheel I99, while therestoring movement of wheel I99 causes cam I92 to-ride of! roller I99(Figs. 21. 23) and permits the spring pressed member I94 to disengagepinion I 99 from wheel I I9.

In the preferred form of the invention, motor 2 of the local time unitassembly is continuously operated while motor I9I for the zone timingunit assembly is normally idle and operated only when one of itsassociated timing units is seized but it will be apparent that bothmotors may be normally idle or normally rotating if desired.

A suitable speed governor is provided for controlling theretum speed ofeach gear wheel. Governor I99 which engages initial wheel I has alreadybeen referred to while a similar governor 229 is provided for overtimewheel II9.

In the particular example of zone timing unit chosen for illustration ithas been assumed that the initial period was five minutes for which themessage register would be operated six times, and that the duration ofeach overtime period was three minutes, for which the message register'would be operated three times. It will be noted mm Fig. 17 that gear I19on pinion I99 is larger than gear II9 on pinion I94 and that overtimewheel I I9 is smaller than initial wheel I99, the relation being suchthat initial wheel I99 makes a complete revolution in five minutes whileovertime wheel II9 makes a complete revolution in three minutes.

- Fig. 29 graphically represents the condition of the various contactsduring the initial and first overtime period for the zone timing unit.Line 22I shows that the locking contacts G are closed at the instant thearmature I49 is attracted at the beginning of the initial period andthat the locking contacts are not broken in going from the initialperiod to the overtime period. Line 229 shows that the holding contactsE are closed shortly after initial wheel I99 starts rotating. are openedshortly before wheel I99 stops rotating and are closed again'shortlyafter overtime wheel II9 starts rotating. Line 224 shows that the oi!-normal contacts I are opened shortly after the initial wheel I99 startsrotating, are closed shortly before wheel I99 ceases rotating and areopened again shortiy=after overtime wheel 9 starts rotating. Line 222shows that the ground contacts F are closed except when the chargingcontacts E are operated. Line 229 shows that the 79 charging contacts Eare operated shortlyafter the holding and oif-normal contacts have beenoperated, to operate six times the message register associatedtherewith, and that shortly after the beginning of each overtime periodthe charging contacts are closed three times.

In the disclosed zone timer it has been assumed that gears I10 and H3are so designed with respect to the speed of shaft I02, that wheel H3completes a revolution once every three minutes and that gears I09 and Hare so designed that the revolution of wheel I09 takes five 'minutes.These gear combinations, however, may be readily altered to give anydesired initial period or overtime period for other zone timingmechanisms which may be required to charge for calls to the variouszones to which the calling subscribers line may be extended. It is alsoobvious that other zone timing mechanisms may have any desired number ofteeth on the initial period charging segment I93 and the overtimecharging segment I94.

Fig. 38 is intended to illustrate certain of the circuits and circuitconnections involved in a cross-bar machine switching system in theselection of the proper timing unit for timing aparticular telephoneconnection. The complete circuits are not disclosed but are shown ingreater detail in the above-mentioned Scudder application.

It will first be assumed that the dialed call is between exchangeswithin the local area. The calling subscribers station 230 will beconnected through the primary and secondary switches of the line switchthrough a district trunk and the district primary and secondary switchesto the called subscribers station 23I. The district trunk relay 238 willbe energized in the usual manner. The dialed information sent to thedecoder marker 232 causes it to connect ground to conductor 235 therebyenergizing relay 234 providing the local timing unit associated with theselected district trunk is in its normal position with its off-normalcontacts B closed. The energization of relay 234 takes place over acircuit from battery, winding of relay 234, conductor 260, closedcontacts B, conductor 235, to ground 236. Relay 234, therefore, pulls upits contacts and is locked up over a circuit from battery, winding 234,left inner front contact relay 234,

- conductor 242, contact relay 238 to ground.

When the called party answers, the called station supervisory relay 231is energized and after a certain delay indicated by the dotted characterof conductor 240 a circuit is established for starting the operation ofthe local timing unit associated with the particular district trunkcircuit employed in. establishing the connection. This circuit may betraced from battery, windingrelay magnet 42, conductors 239, 2, leftmiddle front contact relay 234, conductor 24d, and front contact relay231 to ground. Magnet 42 pulls the pinion 1- into engagement with gearwheel I I' and the local timing unit begins to function to measure theduration of the connection.

between stations 230 and 23L Motor 2 which drives pinion 1 is constantlyoperating as shown in the figure.

Gear wheel II in rotatmg will first open the off-normal contacts B andclose the holding contacts A and shortly thereafter will open groundcontacts D andamomentarily close charging con- Contacts A in closingestablish a holding circuit for relay magnet 42 which may be traced 75from battery, winding relay 42, conductor 239,

closed contacts A, conductor 280, left inner front contact'relay 234,conductor 242, front contact district trunk relay 238 to ground.

With relay 234 energized the normally closed ground contacts D areconnected through conductor 243, left outer front contact relay 234,conductor 244 over the lowest contacts of the primary and secondary lineswitch cross-points, winding message register relay 245, therebyshort-circuiting the message register to prevent its false operation aslong. as the ground contacts D are closed. When wheel II has openedground contacts D and momentarily closed charging contacts C, it willbeobvious that the message register relay 245 will be operated.

Whenever the calling subscriber places his receiver back on theswitch-hook, relay 238 releases, in turn releasing relay 234 which opensthe operating and holding circuits for relay magnet 42. The gear wheelII will thereupon be restored to normal by its restoring spring aspreviously described.

Itwill' now be assumed that the call initiated by the calling station230 is to a station served by an exchange located outside the localarea. The

connections between the calling subscribers district trunk and thedecoder marker are established in the manner described in theabove-mentioned Scudder application. The marker 232 knowing the oflicecode information transmitted to it by the sender (not shown) operatesone of its zone relays such as relay 246, the particular zone relayoperating being dependent upon the zone in which the called stationexchange is lo cated. It will be assumed that shaft I02 is adapted tooperate only one at a time the several zone timing units associatedtherewith, each timing unit being adapted to serve for a different zone,it further being assumed that there are a number of such shafts H12available for selection, each shaft controlling its respective zonetiming units. The decoder marker acting under the dialed oflice codedesignation supplied to it controls apparatus (disclosed in the Scudderapplication) which tests for a zone timing unit assembly which has allof its timing units idle as indicated by the fact that all of theoff-normal contacts of its timing units are closed. It will be notedthat conductor. 241 is connected to battery through the closedoff-normal contacts of all of the timing units associated with thedisclosed zone assembly. Consequently when a test relay (not shown) isoperated when connected to conductor 247 it is indicated that theparticular zone assembly under test is idle and hence available fortiming the call. The marker, therefore, connects ground to that relaymagnet of the zone assembly which is associated with a timing unithaving the proper charging rate for the called zone. Thus, it may beassumed that the timing unit associated with relay magnet I48 is thedesired unit and vhence the marker connects ground to conductor 248leading to winding relay 548, battery and ground, causing relay I48 tooperate. In the meantime the district trunk relay 238 has operated butthe marker does not operate its local relay 249 and hence for a zonecall relay 234 is left unoperated. Also under control of .the marker thecross-bar switch mechanism 258 is operated to connect conductors 25I,252 and 253 to the selected idle zone assembly as will now be described.

Relay magnet I48 when operated serves to engage pinion I 04 with theinitial wheel I 09 but shaft I02 is normally idle. Relay magnet I48 inoperating locks up over a circuit from battery, winding relay I48,locking contacts G, conductors 255, 256, switch 250 and conductor 25I toground. As soon as the called party 23I answers, the called stationsupervisory relay 231 is operated and starts the motor IIII by closingthe following circuit from battery, motor IIlI, conductor 2,54, switch250, conductor 253, left middle back contact relay 234, conductor 24!!and front contact relay'23'l to ground. Motor IIII, therefore, startsrotating shaft I02 and hence the initial wheel I09 starts rotating tomeasure the initial time interval. The movement of wheel I09 first opensthe off-normal contacts I so that no other trunk circuit may seize atiming unit driven by motor I0 I and also closes the holding contacts Hto establish a holding circuit for motor IIII from battery, motor IllI,conductors 254, 251, closed contacts H, conductor 256, switch 250 andconductor 25I to ground.

It will also be noted that switch 250 serves to connect the groundcontacts F to the message register 245 over a circuit which may betraced from ground, closed contacts F, conductor 258, switch 250,conductor 252, left outer back contact relay 234, and the primary andsecondary line switches to the winding of the message register relay245. The continued movement of wheel I09 and cam I93 will open groundcontacts F and close the charging contacts E to connect battery to themessage register. relay a number of times, depending upon the number ofteeth on cam I 93. After wheel I09 has made substantially a completerevolution corresponding to the end of the initial period, wheel I09causes overtime wheel I I3 and cam I94 to start rotating for measuringthe overtime interval. Wheel H3 will also operate the charging contactsE a number of times depending upon the number of teeth on cam I94 aspreviously described, thereby operating the message register 245 inaccordance with the proper charges for eachovertime interval.

When the calling party 230 hangs up, therelease of relay 239 serves toopen the energizing circuits for motor IIII and relay magnet I48whereupon the timing wheels I09 and H3 restore to their normal positionsunder the action of their restoring springs and are, therefore, ready tobe selected for another call.

For convenience in simplifying the schematic showing of the zone timingunit of Fig. 38 one set of ground and charging contacts have been shownfor the initial wheel and another set of ground and charging contactshave been shown for the overtime wheel, but it is to be understood asdescribed in connection with the earlier figures that the preferredarrangement is such that the initial and overtime wheels actuate thesame set of charging and ground contacts. For purposes of simplificationthere is also omitted from Fig. 38 the manner in which the overtimewheel I I3 controls the holding contacts H and ofi-normal contacts I asexplained in connection withFigs. 30 to 37.

What is claimed is:

1. A timing device comprising a driving member, a rotatable drivenmember normally disengaged from said driving member, an electromagnethaving an armature which when attracted controls the engagement of oneof said members with the other of said members, electrical contactsoperated by the advance ofsaid driven member from its normal position,.a tensioned helical spring for restoring said driven member to itsnormal position after disengagement from said driving member, astationary shoulder normally engaging one end of said spring, the otherend of said spring rotating with the rotation of said driven membertending to wind up said spring as said driven member rotates, a cammember driven by said driven member for periodically releasing saidfirst spring end from said shoulder to cause said released end to make arevolution before coming again to rest against said shoulder.

2. A timing device comprising a driving member, a rotatable drivenmember normallydisengaged from said driving member, an electromagnethaving an armature which when attracted controls the engagement of oneof said members with the other of said members, electrical contactsoperated by the advance of said driven member from its normal position,a tensioned helical spring for restoring said driven member to itsnormal position after disengagement from said driving member, astationary cylindrical surface on which one end of said spring rests,the other end of said spring rotating with said driven member, astationary shoulder acting as a stop for said first end to hold saidspring under tension, a cam member driven by said driven member forperiodically releasing said first spring end from said shoulder topermit said first end to complete a revolution about said cylinderbefore again coming to rest against said shoulder.

3. A timing device comprising a driving member, a rotatable drivenmember normally disengaged from said driving member, an electromagnethaving an armature which when attracted controls the engagement of oneof said members with the otherof said members, electrical contactsoperated'by the advance of said driven member from its normal position,a tensioned helical spring for restoring said driven member to itsnormal position after disengagement from said driving member, astationary cylindrical surface on which one end of said spring rests,the other end of said spring rotating with said driven member, astationary shoulder acting as a stop for said first end to hold saidspring under tension, a rotatable cam member for periodically releasingsaid spring end from said shoulder to permit said one end to complete arevolution about said cylinder before again coming to rest against saidshoulder, means rotatable with said wheel for rotating said cam, saidmeans being disengaged from said cam when said driven member is in itsnormal position.

4. A timing device comprising a driving member, a rotatable drivenmember normally disengaged from said driving member, an electromagnethaving an armature which when attracted controls the engagement of oneof said members with the other of said members, electrical contactsoperated by the advance of said driven member from its normal position,a tensioned helical spring for restoring said driven member to itsnormal position after disengagement from said driving member, astationary cylindrical surface on which one end of said spring rests,the other end of said spring rotating with said driven member, astationary shoulder acting as a stop for said first end to hold saidspring under tension. a rotatable cam member for periodically releasingsaid spring end from said shoulder to permit said one end to complete arevolution about said cylinder before again coming to rest against saidshoulder, means rotatable with said wheel for rotating said cam, saidcam member having an elongated arcuate slot for guiding the tricalcontacts actuated by the advance of said wheel from its normal position,a spring stop for determining the normal position of said wheel, meansrotatable with said wheel normally engaging said stop, a tensionedhelical spring for restoring said wheel to its normal position againstsaid stop after the disengagement oi said driving member and said wheel,a stationary cylindrical surface aligned with said axis and on which oneend of said spring rests, the other end oi said spring being rotatablewith said wheel, a sleeve mounted on said wheel for supporting aplurality oi the turns of said spring, a stationary shoulder normallyengaged by said first spring end to hold raid spring undertension, a cammember rotst= able about said axis, said cam member having spacedshoulders, a projection rotatable said wheel and located between saidspacedshoulders, said projection driving said cam member after saidwheel has been moved a substantial distance from its normal position,said cam member after making a substantially complete revolution on saidfirst spring end to release said first spring end from said shoulder topermit said springable driven memberfelectromagnetlc means for movingone of said members into engagement with the other of said members tocause salt driven member to be rotated through a definite angle but notbeyond said angle, electrical contacts for controlling a subscriberscharging cir cult, said contacts being actuatedby said driven memberwhen advanced from its normal position, a second rotatable drivenmember, means under the control of said first driven member for rotateing said second driven member after said first driven member hasadvanced to a definite position, said second driven member during itsrotation also actuating said contacts.

7-. A timing device for measuring the duration 01' a telephoneconnection for which the subscriber is charged at a certain rate for agiven initial period or any fraction thereof and is charged at adiflerent rate for an overtime period, said device comprising a drivingmember, a rotatable driven member, electromagnetic means for forrotating-the same but normally disengaged therefrom, cam means rotatablewithsaid driven member for actuatmc said means to rotation oi saidsecond driven member after said first driven member has reached adefinite advanced position, and means controlled by said second drivenmember for controlling said contacts.

8. A timing device for measuring the duration of a telephone connectioncomprising a rotatable shaft, slidable pinions on said shaft, arotatable wheel, electromagnetic means for moving one oi said pinionsinto engagement with said wheel, a second rotatable wheel, cam meansrotatable with said first wheel-for actuating a second of said pinionsto move said second pinion into engagement with said second wheel whensaid first wheel has reached a definite advanced position, electricalcontacts controlled by said wheels and means for restoring each or saidwheels to a definite normal position when said electromagnetic means hasdisengaged said first wheel from said first pinion" A timing device formeasuring the duration or? a telephone connection comprising a rotatableslidable pinions on said shalt, a rotatable toothed gear wheel,electromagnetic means -for moving one oi said pinions into engagementwith wheel, said wheel having a toothless segment to render said pinioninefiective alter said wheel has been advanced to a definite no time, asecond gear wheel, means controlled by the adoi said first wheel forcausing a second pinion to engage said second wheel, electricalconcontrolled by said wheels and means for restoring each oi said wheelsto a definite normal position when said electromagnetic means hasdisengaged said first pinion from said first wheel.

ii). device for measuring the duration on? a telephone conversationcomprising n rotatable shalt, gears driven by said shaft, a rotatabledriven: member comprising a gear wheel, electromagnetic means forengaging said wheel with one of said gears, said wheel having atoothless segment to render first gear ineffective after said wheel hasbeen advanced to a definite position, spring means for preventingcontact between the teeth on said wheel and the teeth on said first gearwhen said first gear reaches said toothless segment, a second rotatabledriven member comprising a second gear wheel, means controlled by saidfirst member for engaging said second scriber is charged at a certainrate for a given initial period 1 any fraction thereof and is charged ata certain rate for an overtime period,

, said device comprising a drivingmember, a rotatable driven member formeasuring said initial period, a. rotatable driven member tor measuringsaid overtime period. electromagnetic means 101 en a ing said drivingmember and said initial member, means for disengaging said drivingmemand said initial member after said initial member has rotated for atime interval substantially equal to said initial period, meanscontrolled by said initial member andeflective only after said initialmember has advanced sumciently to substantially complete the measurement of said initial period tor ensaflne said driving member and saidovertime member, said initial member and said overtime member each ingmember from their normal positions, and being biased to a deiinitenormal position, elecmeans eii'ective alter the disensagement 0! saidtrical contacts for controlling a subscriber's driving member andinitial member for holding charging circuit and actuated both by saidinitial said initial member in its advanced position durmember and saidovertime member when said ing the time interval said driving member isin 5 initial member and said overtime member are engagement with saidovertime member.

advanced a predetermined amount by said drlv- EDWARD D. MEAD.

